Catheters are being used increasingly as a means for delivering diagnostic or therapeutic agents to internal target sites that can be accessed through the circulatory system. There are a number of general approaches for placing catheters within vessels in the body that are difficult to access. In one such technique, a torqueable guidewire is alternately rotated and advanced to the target site. With the wire in place, the catheter is then advanced along the wire until the distal end of the catheter is positioned at the target site. An example of this technique is described in U.S. Pat. No. 4,884,579. A major drawback to this approach is the time-consuming nature of rotating and advancing the guidewire and catheter through the vasculature.
A second technique for advancing a catheter to a target site is to employ a highly flexible catheter having an inflatable, but pre-punctured balloon at its distal end. In use, the balloon is partially inflated, and carried by blood flow into the target site. During placement, the balloon is continually inflated to replenish fluid leaking from the balloon. This technique, too, has major drawbacks including the fact that the catheter material is so floppy that it cannot be pushed without buckling, and instead must be advanced using injected fluid to inflate the balloon in order to propel the catheter to the target site. Additionally, there is a significant risk of rupture of a vessel by a balloon that has been overinflated.
In order to address some of the above described problems, another approach has involved the use of flexible catheters that can be directed to a target site as a result of the blood flowing to that site. In 1991, Target Therapeutics released a product known as the "ZEPHYR" flow-assisted infusion catheter. The product was designed to be introduced into the vasculature through a guiding catheter and then allowed to be directed by the blood flow to a target site. The catheter comprised segments of different materials, a proximal segment made of nylon, and middle and distal segments made of a block copolymer of polyamide. The product proved to be unsuccessful in achieving its desired function as it was not flexible enough to navigate the tortuous vessel pathway and not strong enough to withstand the required injection pressure.
The present invention is an infusion catheter assembly useful for the delivery of diagnostic, therapeutic or vasoocclusive agents to remote portions of the vascular system, particularly to diagnose or treat arteriovenous malformations (AVMs). The invention also includes a process for placing the infusion catheter at the target site and a process for delivering a diagnostic, therapeutic or vasoocclusive agent to the target site.